What is the term referring to the synergistic action of muscle groups to produce movement around a joint?

The answer is the force –couple, this is a group of muscles that moves around the joint and this move to produce movement. A couple involves of two parallel forces that are equal in magnitude, opposite in sense and do not share a line of action. This is a pure moment and single force acting at a single point. 

lizards have adapted to life in the desert. some desert lizards have toes with spiny scales to them run across the sand without sinking. some use the sand to hide from predators, or to search for small animals that they prey upon.